The present invention relates to fuel tank jet pumps, which are used in an automotive vehicle, to transfer fuel from a fuel supply tank, to a fuel tank conditioning reservoir, prior to delivery to the vehicle fuel system. In particular, the variable orifice, pressure compensated jet pump of the present invention maintains close to peak operating efficiency in situations where the fluid viscosity range is broad, or where the driving flow rate varies significantly.
Conventional jet pumps used for automotive applications are usually of the fixed orifice type. When used with fluids having a narrow viscosity range, as well as a supply pressure with minimal variation, the jet pump will have a flow rate also with minimal variation. Minimal flow rate variation maintains an almost constant velocity in the driving fluid jet. The above-noted properties enable conventional jet pumps to be designed to operate in a narrow range, at reasonable efficiency.
Jet pumps are typically used to maintain fuel in a fuel tank conditioning reservoir (commonly referred to as a fuel delivery module) inside the fuel tank, just prior to fuel delivery to the vehicle fuel system. Jet pumps may also be used to transfer fuel from a secondary fuel tank to a main fuel tank or from a secondary fuel reservoir to a main reservoir, in multi sump or saddle-type fuel tanks.
Jet pumps are normally driven by a fuel bleed from a fuel feed pump system. This fuel feed pump system typically has minimal variation in pressure, as well as having more than adequate flow capacity for the main fuel system, such that excess flow can be taken to drive the jet pump(s). Where fuel feed pump capacity is marginal, the fuel returned from the fuel system may be used to drive the jet pump(s), but occasionally with some loss in peak efficiency, due to the possible fuel return line flow variation.
If the fixed orifice jet pump is used with fluids having a broad viscosity range (due to fluid composition variations or variations in fluid temperature), the efficiency variation of the jet pump will be much greater. Also, using a fixed orifice jet pump on a fuel return system, where the fluid flow rate can vary significantly, may cause excessive system back pressure, unless a pressure relief valve is added.
It is desirable to provide a variable orifice, pressure compensated jet pump which will not only prevent the excessive back pressure, but will adjust the orifice to handle the variation in flow and viscosity, maintaining a near constant driving fluid velocity, which will keep the fuel jet pump working close to its peak efficiency.
It is additionally desirable to provide a variable orifice, pressure compensated fuel jet pump which can be used with the fuel system return flow driving the jet pump, even if the flow varies significantly, while controlling (limiting) the back pressure in the fuel return line.
To make manifest the above delineated and other desires, the revelation of the present invention is brought forth. In a preferred environment, the present invention provides a diesel powered automotive vehicle fuel system which includes a fuel tank with multiple control volumes. The fuel tank has a first control volume or fuel module and a second control volume. A first source of pressurized diesel fuel typically provided by an injector servo return, high pressure pump coolant fuel return, or a branch line from the fuel feed pump is connected with a pressurized fuel supply line having an outlet. The outlet of the pressurized fuel supply line is fluidly connected with a first chamber. The first chamber has a rear end which is sealed from a front end by a spring-biased diaphragm. The front end of the first chamber has a nozzled outlet. A second chamber is provided opposite the first chamber having an inlet in fluid communication with the first chamber outlet. The second chamber has an outlet fluidly connected with the first control volume. The second chamber also has an inlet fluidly connected with the second control volume. The first and second chambers cooperate to provide a jet pump to deliver diesel fuel from the second control volume to the first control volume. A valve member operatively associated with the spring-biased diaphragm is fixably connected thereto. The valve member has a head which gives the nozzle of the first chamber a variable opening orificed area. The valve member by virtue of its connection with the diaphragm, is sensitive to pressure differentials between the first chamber front end and the first chamber rear end. The rear end of the first chamber is exposed by fluid connection with the second volume. Accordingly, the valve member functions to maintain an approximate constant fuel flow velocity through the nozzle of the first chamber. Accordingly, efficiency of the jet pump is maintained regardless of the fuel viscosity and flow rate that is delivered to the first chamber via the pressurized fuel source.
Not only is the efficiency of the jet pump maintained over various viscosity ranges of the diesel fuel, but the back pressure of the system can be held sufficiently that low back pressure tolerant injector fuel returns associated with high pressure common rail diesel injection systems can be utilized to provide the pressurized fuel source.
It is a feature of the present invention to provide an automotive vehicle fuel system having a jet pump to deliver fuel from a second control volume to a first control volume utilizing a jet pump which is pressure compensated.
It is also a feature of the present invention to provide an automotive vehicle fuel system having a saddle tank with a jet pump to deliver fuels with variable viscosity, such as diesel fuel, from a secondary control volume to a first control volume of the fuel tank. The system utilizes a pressure compensated jet pump which automatically adjusts to maintain the fuel velocity through the jet pump at a constant velocity to maintain the efficiency of the jet pump during various changes in the fuel viscosity.
The above-noted features and other advantages of the present invention will become more apparent to those skilled in the art as the invention is further explained in the accompanying drawings and detailed description.